This invention relates to an internal combustion engine and more particularly to an improved induction control system for a direct injected engine.
The continued demand for higher performance and more efficient and lower emission internal combustion engines has prompted the widespread use of fuel injection as a method of charge forming. By utilizing fuel injectors, a number of benefits can be gained. Among these include the ability to more accurately control the amount of fuel delivered, particularly on a cycle-by-cycle basis.
Most production engines that employ fuel injection, however, employ a system which is referred to as "manifold injection." With this type of arrangement, the fuel is injected into the intake passage generally in proximity to the intake port that serves the combustion chamber. This system permits the use of lower cost fuel injectors and still obtains many of the benefits of fuel injection.
However, it is generally necessary to have a homogeneous fuel air mixture in the combustion chamber. This is done to insure combustion at the appropriate timing. This is particularly true in conjunction with spark ignited engines. As a result of this, there is actually more fuel in the combustion chamber than is necessary to obtain the desired power under most running conditions. Thus, there gives rise to the problem of higher than necessary fuel consumption and also greater than desired exhaust gas emissions.
Therefore, there has been a desire to obtain an engine that can run in a so-called "lean burn" mode. This involves fling the cylinder with a less than stoichiometric mixture under all but high speed, high load running conditions. If this can be achieved, then further improvements in fuel economy and exhaust emission control can be obtained.
One way of obtaining the capability of lean burning is if the charge in the combustion chamber is stratified. Although stratification can be easily obtained utilizing pre-combustion chambers, these chambers give rise to pumping losses and have other disadvantages. Therefore, there is a desire to be able to obtain stratification in an open chamber engine. Direct cylinder fuel injection lends itself to achieving this goal.
However, there is still a difficulty in insuring that the appropriate fuel air mixture is present at the spark plug at the time of firing. Also, there is a desire to increase the turbulence in the charge at low speeds and low loads so as to insure good flame propagation.
It is, therefore, a principal object of this invention to provide an improved internal combustion engine having direct cylinder injection and wherein lean burning through stratification can be accomplished.
It is a further object of this invention to provide an improved arrangement for introducing a fuel air charge into the combustion chamber of an engine that will ensure good burning under all running conditions.
In connection with the generation of turbulence in the combustion chamber, this is desirable in order to obtain good flame propagation under low speed low load conditions. Most turbulence generating devices, however, restrict the amount of airflow and hence, the power output of the engine will be reduced.
It is a further object of this invention to provide an improved turbulence generating arrangement for the induction system of an engine wherein high speed high load output are not sacrificed.
In addition to desiring turbulence in the combustion chamber, another problem that is attendant with direct fuel injection is the difficulty of confining the location of the injected fuel. Obviously, the fuel must be injected at a fairly high pressure so as to insure that adequate will be present to serve all running conditions. This high pressure spray, however, is somewhat difficult to control.
It is, therefore, a still further object of this invention to provide an improved induction passage arrangement for a direct injected engine wherein the induction passage assists in controlling the direction of fuel spray and increasing turbulence without significantly reducing the amount of fuel spray.